Method and machine for determining unbalance of rotating workpieces



March 5, 1963 H. HACK 3,079,801

METHOD AND momma FOR DETERMINING UNBALANCE OF ROTATING WORKPIECESOriginal Filed Sept. 2, 1958 2 Sheets-Sheet 1 I 28 30 129 I [9 /6 5/7 94 l 7 I 80 I 1 12 f5 -I3a a9 I 23 LLVWLQ/AJ M H. HACK March 5, 19633,079,801 METHOD AND MACHINE FOR DETERMINING UNBALANCE OF ROTATINGWORKPIECES Original Filed Sept. 2, 1958 2 Sheets-Sheet 2 weight or theunbalance-to-weight quotient.

vMy invention is' disclosed and claimed herein as a continuation of mycopending application Serial No. 753,428, filed September 2, 1958, to beabandoned after the filing date of the present continuation.

The invention relates to machines for determining unbalance of rotatingworkpieces by'means of devices that respond to oscillations caused bysuch unbalance and that convert such oscillations-into characteristicphysical values, such as electric voltages, indicative of the magnitudeand angular position of the unbalance. These voltages or other physicalcriteria indicative of the unbalance,

are supplied to receiving devices where they are utilized forindicating,srecording or controlling purposes. The unbalance criteriaresults from the displacement of the gravity center ofthe workpiecewhich displacement is constituted by the quotient of the unbalance andthe weight of theworkpiece. Hence, for calibrating the indicating: orrecording instruments, the known methods and devices require performinga preliminary calibrating run of the workpiece with an intentionallyadded, known unbalance for determining the effect of the workpiece Thisadditional calibrating run is undesirably time-consuming particularlywhen ditlerent individual workpieces or only small series of workpiecesare to be balanced.

It is an object of my invention to devise means which aflord' anabsolute determination of the unbalance of a rotating body irrespectiveof its weight. Another object, akin to the one just mentioned, is toprovide means for determining the unknown unbalance of various rotatableworkpieces that may greatly differ from each other in weight, withoutrequiring a re-setting of the balanceanalyzing equipment when changingfrom a workpiece of one weight to a workpiece of difierent weight.

To this end, I proceed by forming a quotient from 'two differentunbalance criteria, namely one criterion,

such as the output voltage of an oscillation pickup, characteristic ofthe unbalance (U) of the rotating Workpiece under observation, andanother criterion which is characteristic of the sum (U') of theunbalance (U) of the workpiece plus a known unbalance magnitude (U whichmanifests itself by oscillations in synchronism and in phase with theunbalance (U) of the workpiece. The

- then is proportional of the workpiece unbalance regardknown unbalance(U in rotation upon a carrier which,

like the journalling structure for the workpiece, is oscillatorilysupported so that the known unbalance of the rotor excites the carrierto oscillations which are added to'those of the workpiece journallingstructure by means of a mechanical coupling of a given direction.Applicable instead of a rotating auxiliary rotor of known unbalance,

tats aent vtion to the machine sstassi is any other suitable oscillatoror magnetic exciter capable of producing sinusoidal referenceoscillations equivalent to those produced by the known unbalance.

The equation of the above-mentioned quotient indicative or" the unknownunbalance irrespective of the weight of the workpiece can vbe expressedas:

-cos o For =0 this equation can be written as wherein According tofurther features of my invention, a preferred machine for performingthe-above'described method is provided with a supporting structure withjournal means for accommodating the shaft on which the workpiece isrotatable, the supporting structure being connected-with the rigid andfixed frame structure of the machine by spring means that permit thestructure, when excited by unbalance of the workpiece during rotation ofthe latter, to'perforrn oscillations in a given plane parallel tothat ofthe workpiece rotation. The means for driving the workpiece arepreferably mounted on the oscillatable supporting structure, and thepickup means for response to the oscillations aremounted in fixedrelarame structure. I further provide the machine with anotheroscillatingly supportedstructure or carrier on which another body,herein called rotor, is journalled for rotation in a plane parallel tothat of the workpiece rotation, this rotor having an unbalance of knownmagnitude; During operation of the rotor, the carrier is excited tounbalance-responsive 0scillations but it can oscillate only in aplanealso parallel to that of the workpiece rotation. The supportingstructure for the workpiece and the carrier for the rotor are coupledwith each other for transmission of oscillations in a given direction soas to produce in said given direction a resultant oscillationcorresponding to the sum of the unbalance effects caused by theworkpiece unbalance plus the known unbalance of the rotor. The unbalanceoscillations of the workpiece-journflling structure are converted by asuitable oscillation pickup into a physical magnitude, for exmple anelectric alternating voltage, indicative of the workpiece unbalancealone. The resultant oscillations in the above-'nentioned givendirection, caused by sum of workpiece unbalance plus known unbalance,are converted by another pickup into another criterion, such as anelectric voltage, indicative of these resultant oscillations. I furtherconnect a ratio-measuring device with both oscillation pickups so thatthe device supplies output magnitude, such as a resultant voltage, whichis proportional to the quotient of the two unbalance criteria. Thisoutput magnitude is indicative of the workpiece unbalance irrespectiveof the weight of the workpiece and can be indicated recorded or used forcontrol purposes, such as for controlling the operation of anunbalance-correcting machine tool.

In such a machine according to the invention, the workpiece-journallingstructure is preferably formed by a housing which is supported on therigid base of frame structure of the machine by means of spring rods sooriented that the housing and all components connected therewith canoscillate only in a single plane parallel to the plane of workpiecerotation. The p'ckup devices and preferably the quotient-measuringdevice are preferably mounted on the rigid frame structure in such amanner that the two pickups respond to oscillations in two respectivedirections of which one is parallel to the abovementioned givendirection of coupling between journallin g structure and rotor carrier,and the other is perpendicular thereto. For determining unbalance inseveral planes, the above-described devices are to be duplicated orotherwise modified, for example by using a so-called isotropic supportof the workpiece-journalling structure and by using a correspondingnumber of auxiliary rotors or other excitation devices.

While according to the above-described preferred embodiment of a machineaccording to my invention, the oscillatory effect of a known unbalance(U is produced by a rotor whose unbalanc -responsive oscillations aretransmitted preferably by spring rods onto the journalling support forthe workpiece, it is also within the scope of my invention to use othertypes of oscillators for producing an oscillation equivalent to theknown unbalance.

The invention will be more fully understood from the embodiment of abalancing machine for determining unbalance in a single planeschematically illustrated by way of example on the accompanying drawingon which- FIG. 1 is a partly sectional front view of the machine andalso shows schematically an appertaining electric circuit diagram insingle-line representation,

FIG. 2 is a top view of the same machine, and

PEG. 3 is an electric circuit diagram corresponding to FIG. 2.

The workpiece 1 is mounted on a shaft 2 connected or integral with theshaft of an electric motor 3. The motor 3 is flanged or otherwiserigidly joined together with a housing structure 4 which is supported onthe rigid base or frame structure 6 of the machine by means of sprin"rods 5 so oriented that the housing 4 is capable of oscillating relativeto the rigid frame structure 6 only in a plane, or in planes parallel tothat of the workpiece rotation. Mounted on the rigid frame structure 6are electric oscillation pickups 7 and 8 whose respective feeler rods 9engage the housing structure 4 in order to convert theunbalance-responsive oscillations of the housing into respectiveelectric voltages. The pickup axes extend in mutually perpendiculardirections Within respective planes parallel to that of the workpiecerotation. Joined with motor 3 is a synchro-generator 11 which is coupledwith the motor shaft to run in synchronism with the workpiece.

The synchno-generator 11 is electrically connected through a controlswitch 22' and a lead 12a with a synchro-receiver 12 and produces athree-phase field current which is supplied to the synchro-receiver 12to cause the receiver to place its shaft 1212 into the same angularposition as the one occupied by the shaft of the synchrogenerator 11.The generator 11 and the receiver 12 thus form together analternating-current synchro-link, operating as an angular-positiontransmitting device. Details of the synchros 1i and 12 and theirinterconnection are not further described in this specification becausesuch synchro-links are generally known and are available in the trade,for example under the trade name Selsyn or Synchrotie. A description andexplanation of such synchro-d-evices may be found, for instance, in thebook Analysis of Feedback Control Systems by Robert A.

Bruns and Robert M. Saunders, McGraw-Hill Book Company, Inc, New York,1955, Chapter 10.3 A.-C. Synchros, page 188 and following. if desired,reference may also be had to my co-pending patent applications Serial,ovasc d No. 606,929, filed August 29, 1956, now US. Patent No.2,933,984, and Serial No. 743,350, filed June 20, 1958, both assigned tothe assignee of the present invention, Where suitable synchro-links areillustrated and described in detail.

The shaft 12b of the synchro-receiver 12 carries a spur gear 17 whichmeshes with a spur gear 18 fixed to the stator or housing of asynchronous drive motor 19. Mounted on the shaft of motor 19 is adisc-shaped rotor which carries an unbalance member 29 of known magnitude. Tne synchro-receiver 12 and the drive motor 19 are mounted in acommon housing 39. This housing, hereinafter called carrier, issupported on the rigid frame structure 6 of the machine by means of leafsprings 31, 32, so as to be capable of oscillations in only one planewhich is parallel to the plane of workpiece rotation and corresponds tothe plane of illustration in FIG- 2. While the stator ofsynchro-receiver 12 is firmly joined with the carrier 36, the stator ofdrive motor 19 is rotatable within carrier 3% and for that purpose ismounted in ball bearings 2i and 21.

When commencing the balancing operation, with workpiece 1 mounted onshaft 2, the rotor of the synchrogenerator 11 is excited by directcurrent which, at that stage of operation, is supplied from adirect-current source B through a switch 2.2" and a lead 11a. The rotorof the synchroreceiver 12 receives alternating voltage from oscillationpickup 8 through a lead 39, an amplifier 13, and a lead 130. Under theseconditions, the rotor of synchro-receiver E2 and thus the shaft 12badjust themselves in accordance with the angular position of theunbalance of workpiece 1. This position is indicated on a scale 15 bymeans of an indicating device 14 connected with the shaft 12b. Theposition is then fixed by actuating a magnetic clutch or brake 16.

Since the shaft 12b of synchro-receiver 12 is coupled through spur gearsl7, 18 with the stator of motor 19, this stator is now also set relativeto carrier 36), to an angular position which corresponds to the angularposition of the workpiece unbalance.

After the workpiece unbalance and the auxiliary unbalance 29 are thusset to in-phase position, a switch, comprising the contact 22', 22 and22", is actuated. As a result, the synchro-generator 11 is disconnectedat con tact 22 from the synchro-receiver 12 which then becomes inactivewith its shaft 12b kept arrested by clutch 16 in the adjusted position.At the same time, the contact 22' now connects the output of thesynchrogenerator 13. through a lead 19a with the synchronous drive motor19, and contact 22 disconnects the direct-current source D rrc-mtherotor of the synchro-generator 11 and instead connects it with analternating current source A. As a result, the drive motor 19 now runsin synchronism with he generator 11 and hence in synchronism with theworkpiece 1 as soon as the latter is driven and brought to the normalbalancing speed by means of the drive motor 3.

' Under such conditions, the auxiliary unbalance caused by the weightmember 29 is synchronized in Zero-phase relation with the workpiece sothat the oscillations to which the structure 4 on the one'hand and thecarrier 3i? on the other hand are excited by the workpiece unbalance andthe known unbalance respectively are in phase with each other.

The carrier 3 and the structure 4 are mechanically coupled with eachother by a spring rod 33 which extends in a horizontal directionparallel to the active direction of the above-mentioned pickup. Theconnecting rod 33 in coaction with the leaf-spring supports 31, 32 hasthe effect that the oscillations of the carrier 30 caused by the knownunbalance are cumulatively related to the oscillation component of thestructure caused by the workpiece unbalance in the same direction.Consequently, this directional component of the unbalance-responsiveoscillations of structure 4 is dependent upon, and characteristic of,the sum of the two unbalance effects. Conthe above-mentioned quotient.

FIG. 1 is of the dynamoelectric type.

aerosol sequently, the electric voltage generated by the pickup nentoscillations of the structure 4 that are caused by the unbalance of theworkpiece 1. Consequently, the voltage generated by pickup 8 ischaracteristic of the workpiece unbalance only.

The two voltages of the respective pickups 7 and 8 are supplied to aratio-r .easuring instrument 37 for forming While variou types ofquotient-computing devices are available and applicable, the onepreferably used and schematically illustrated in it comprises twostationary field coils 25 and 26, and two moving coils 33 and 43 mountedon the same spindle and cooperating with thecoils 25 and 26respectively. The spindle of the moving coils carries a'pointerlcooperating with a scale 42 graduated invalues of quotient, orpreferably directly in magnitudes of unbalance of the workpiece.

The two moving coils 3S and 3%. are energized through respective leads37 and 39 by the voltages generated by pickups 7 and 8 respectively. Thefixed coils 25 and 26 receive sinusoidal current from av phase referencegenerator 19 through respective leads 23 and 24. The phase referencegenerator is shown coupled with the shaft of motor 19 to operate insynchronism with the workpiece rotation so that thecurrents generated bygenerator '19 are also in synchronism with the workpiece rotation. itwill be understood that the phase reference generator 19, if desired,may also be connected with the shaft 2 of motor 3 because it is onlyessential that the generated sinusoidal currents be synchronized withthe workpiece rotation. The reference generator 19', as well known inthe balancing art, produces two sinusoidal voltages 90 phase displacedfrom each other. Thus, the lead 23 supplies the coil '25 of thequotient-forming device 27 with a sinecurrent, whereas the lead 24supplies the coils 26 of the same device 27 with a cosine current. Asexplained above, the magnitude indicated by thesquotient-forming device27 is indicative of the unbalance of the workpiece i irrespective of theweight of the workpiece, arrdthe machine is capable of accuratelyindicating unbalanceeven if the workpiece is substituted by a workpieceof different weight, without requiring calibration or resetting of themeasuring equipment.

In machines intended for rotating the workpiece at supercritical speeds,the mass of the machine components participating in theunbalance-responsive oscillation may affect the measuring result. Forthat reason, the illustrated machine is provided with an auxiliary mass34 which is connected withthe rigid frame structure by leaf springs 35and 36 so as to be capable of performing oscillations relative to theframe structure in a plane parallel to that of the workpiece rotation.The weight of mass 3-iis preferably made substantially equal to-the sumof the weights of the parts that produce the known-unbalanceoscillations of carrier 39; The auxiliary mass 34 is coupled by a springrod 43 with the workpiece-journalling structure 4, the spring 43extending in a direction parallel to the active direction of pickup 8.The auxiliary mass permits compensating the mass inertia movements ofthe exciter housing 353 in the active direction of-the oscillationpickup 3.

It will be apparent to those skilled in the art upon studying thisdisclosure, that machines according to the invention permit a variety ofmodifications and hence may be embodied in design other than the oneillustrated and particularly described herein, without departing fromthe essence of my invention and within the scope of the claims annexedhereto.

I claim:

1. A machine for determining unbalance of a rotating workpiece,comprising an oscillatorily mounted structure having shaft means forrotating the workpiece onsaid structure, said structure being capableofoscillation in a plane parallel to that of the workpiece rotation inresponse to unbalance of the workpiece, an auxiliary'oscillatorcorresponding to a known unbalance, synchronizing means interconnectingsaid shaft means and said oscillator for synchronizing the'respectiveoscillations of said structure and said oscillator in phase with eachother, said oscillator being mechanically coupled with said structurerelative to a given direction whereby said respective oscillationscombine to a cumulative resultant oscillation in said direction, a firstoscillation pickup responsive to said resultant oscillation insaiddirection to furnish an output substantially corresponding to the sum ofthe workpiece unbalance plus said knownunbalance, a second oscillationpickup responsive to oscillation of said-structure to furnish an outnutsubstantially corresponding to the workpiece unbalance'only, andquotient-forming device connected to said two pickups: andresponsivetosaid two pickup. outputs, whereby said device forms aquotient whose value is indicative of the workpiece unbalance regardlessof the weight of the workpiece.

2. A machine for determining unbalance of a rotating workpiece,comprising an oscillatorily mountedstructure having shaft meansfor'rotating the workpiece ons'aid structure, said structure being'capableof oscillation in a plane parallel to that of the workpiece rotationinresponse to unbalance of. the workpiece, a carrier oscillatorilymounted and capable of oscillation in a. given direction of a planeparallel to that of the workpiece rotation, an auxiliary rotor of knownunbalance journalled on said carrier for rotation in a plane paralleltot-hat of the workpiece rotation, said carrier and said structure beingmechanically coupled for joint oscillatory motion in said givendirection whereby the. respective'unbalanceresponsive oscillations ofsaid structure and said carrier combine themselves to a resultantoscillation in said'given direction, synchronizing means interconnectingsaid'shaft means and said rotor for rotating them simultaneously withsaid workpiece unbalance and known unbalance in phase with each other,'afirst oscillation pickup. responsive to said resultant oscillation insaid given direction, a second oscillation pickup responsive tooscillation of said structure in another direction coordinately relatedto said given direction to respond substantiallyionly to saidworkpieceunbalance, aquotient-forming device connected to said two pickups toform a value corresponding to-the workpiece unbalanceindependently ofthe-weight ofzthe workpiece.

3. A machine for determining unbalance of a rotating workpiece,comprising an oscillatorilymounted structure having shaft means forrotating the workpiece on said structure, said structure being capableof oscillation in a plane parallel to that of the workpiece rotation inresponse to unbalance of the workpiece, a carrier oscillatorily mountedand capable of. oscillation in a given direction of a plane parallel tothat of the workpiecerotation, an auxiliary rotor of known unbalancejournalled on said carrier for rotation in a plane parallel to that ofthe workpiece rotation, said carrier and said 5 octure beingmechanically coupled forjointoscillatory motion in said given directionwhereby the respective unbalance-responsive oscillations of saidstructure and saidcarriercombine themselves to a resultant oscillationin said given direc- -tion, synchronizing means; interconnecting saidshaft means and said rotor for rotating them simultaneously, phase shiftmeans interposed between .said shaft means and said rotor for adjustingthe phase angle between the workpiece unbalance and said known unbalanceto zero, a first oscillation pickup responsive to said resultantoscillation in said given direction, a second oscillation pickupresponsive to oscillation of said structure in another directioncoordinately related to said given direction to respond substantiallyonly to said workpiece unbalance, a quotient-forming device connectedto, said two pickups to form a value corresponding to the workpieceunbalance independently of the weight of the workpiece.

4. In a machine according to claim 2, said synchronizing meanscomprising an alternating-current generator mounted on said structureand coaXi-ally joined with said shaft, and a synchronous motor mountedon said carrier and mechanically coupled with said rotor, said motorbeing electrically connected with said generator to be synchronouslydriven therefrom.

5. A machine according to claim 2, comprising a rigid machine frame, twosets of springs fastened to said frame and joined with said structureand said carrier respectively whereby said structure and said carrierare independently oscillatable relative to said frame, and spring-rodmeans interconnecting said structure and said carrier for coupling themto oscillate together in said given direction.

6. In a machine according to claim 3, said phase-shift means comprisinga synchro-generator mounted on said structure and co'axially connectedwith said shaft, and a synchro-receiver electrically connected to saidsynchrogenerator and mounted on said carrier, said synchroreceiver beingmechanically coupled with said rotor for placing its known unbalance tozero-phase position relative to the workpiece unbalance.

7. In a machine according to claim 3, said phase-shift means comprisinga synchro-generator mounted on said structure and coaxially connectedwith said shaft, and a synchro-receiver electrically connected to saidsynchrogenerator and mounted on said carrier, said synchroreceiver beingmechanically coupled with said rotor for placing its known unbalance toZero-phase position relative to the workpiece unbalance, and anindicating device connected with said synchro-rnotor for indicating thephase angle between said respective unbalances.

8. A machine for determining unbalance of a rotating workpiece,comprising an oscillatorily mounted structure having shaft means forrotating the workpiece on said structure, said structure being capableof oscillation a a plane parallel to that of the workpiece rotation inresponse to unbalance of the workpiece, a carrier oscillatorily mountedand capable of oscillation in a given direction of a plane parallel tothat of the workpiece rotation, an auxiliary rotor of known unbalancejournalled on said carrier for rotation in a plane parallel to that ofthe workpiece rotation, said carrier and said structure beingmechanically coupled for joint oscillatory motion in said givendirection whereby the respective unbalanceresponsive oscillations ofsaid structure and said carrier combine themselves to a resultantoscillation in said given direction, a synchro-genera-tor mounted onsaid structure and coaxially connected with said shaft, a drive motormounted on said carrier for rotating said rotor in synchronism with saidshaft when energized from said generator, said drive motor having astator angularly displaceable about its axis relative to said carrier,at synchro-receiver also mounted on said carrier and mechanicallycoupled with said stator for angularly displacing it when saidsynchro-receiver is energized from said generator, selective switchmeans for connecting said generator first to said synchro-receiver toset the phase angle between workpiece unbalance and known unbalance tozero and then connecting said generator to said drive motor for drivingsaid rotor in synchronism with the workpiece, a first oscillation pickupresponsive to said resultant oscillation in said given direction, asecond oscillation pickup responsive to oscillation of said structure inanother direction coordinately related to said given direction torespond substantially only to said workpiece unbalance, and aquotient-forming device connected to said two pickups to form a valuecorresponding to the workpiece unbalance independently of the weight ofthe workpiece.

9. A machine according to claim 8, comprising directcurrent supply meansand alternating current supply means, said switch means having a firstposition in which it connects, said direct-current supply means to saidgen- 8 erator to provide synchro-field excitation thereto and connectssaid generator to said synchro-motor, and said switch means havinganother position wherein it connects said generator with saidalternating-current supply means and connects said drive motor with saidgenerator for operating said drive motor.

10. In a machine according to claim 3, 'said two pickups consisting ofelectric transducers for converting the unbalance-responsiveoscillations to respective voltages, and said quotient-forming devicehaving two electric input circuits connected to said respective pickupsto be energized by said respective voltages.

11. A machine according to claim 3, comprising a. phaseueferencegenerator for providing two sinusoidal reference currents of phasedisplacement relative to each other, said phase-reference generatorbeing mechanically connected with one of said shaft and rotorrespectively whereby said currents are synchronous with the workpiecerotation, said two pickups consisting of electric transducers forconverting the unbalance-responsive oscillations to respective voltages,and said quotient-forming device having an electrodynamic systemcomprising two stationary field coils and two moving coils coacting withsaid respective stationary coils and having a common mounting spindle,said stationary coils being connected with said phase-referencegenerator to be traversed by said respective two currents, and saidmoving coils being connected to said respective pickups to be excited bysaid respective voltages.

12. A machine according to claim 2, comprising a rigid machine frame onwhich said structure and said carrier are oscillatorily mounted, saidtwo pickups being firmly connected with said frame, an auxiliary bodywhose weight corrcsponds approximately to that of the means forproducing the known unbalance, said body being oscillatorily mounted onsaid frame for oscillation in a plane parallel to that of workpiecerotation, and means linking said body with said structure in a directionparallel to the active direction of said second pickup.

13. A machine for determining unbalance of a rotat- 'ing workpiece,comprising a journal structure for rotatably mounting the workpiece,drive means for rotating the workpiece to produce oscillations of saidstructure due to unbalance of the workpiece, an auxiliary oscillatormechanically coupled with said structure for subjecting it to a knownunbalance caused by said oscillator, said oscillator having means forphasing said oscillator to phase coincidence of the respectiveoscillations of said structure and said oscillator, oscillationexpansive measuring means for measuring an unbalance criterion of theworkpiece, measuring means for simultaneously measuring a correspondingunbalance criterion of the combined unbalances of workpiece andoscillator, quotient-forming means connected to said two measuring meansfor forming a quotient of both criteria, whereby said quotient isindicative of the workpiece unbalance regardless of the weight of theworkpiece.

14. The method of determining unbalance of a rotating workpiece, whichcomprises rotating the workpiece about its axis to obtain oscillationsin a plane transverse to the axis due to the workpiece unbalance to bedetermined, simultaneously imparting to the workpiece in a givendirection parallel to said plane an auxiliary oscillation of knownamplitude and phasing said auxiliary oscillations for phase coincidencewith the unbalance oscillations, sensing an unbalance criterion of theworkpiece in a direction angularly related to said given direction insaid plane and simultaneously sensing substantially in said givendirection a corresponding oscillation criterion of the combinedunbalance oscillation and auxiliary oscillation, and forming a quotientof both criteria, whereby said quotient is indicative of the workpieceunbalance regardless of the weight of the workpiece.

15. The method of determining unbalance of a rotating workpiece by meansof devices which produce criteria indicative of magnitude and angularposition of the unbalance, which comprises rotating the workpiece toproduce mechanical oscillations in a plane transverse to its axis due tounbalance of the rotating workpiece, simultaneous ly imparting periodicauxiliary oscillation to the workpiece in a given direction parallel tosaid plane and phasing said auxiliary oscillations to phase coincidencewith the respective unbalance oscillations, sensing an unbalancecriterion of the rotating workpiece in a direction angularly related tosaid given direction in said plane and translating said criterion intoan electric magnitude, simultaneously sensing in said given direction acorresponding unbalance 16 criterion of the combined unbalanceoscillations and auxiliary oscillations and translating it into anotherelectric magnitude, and electrically forming a quotient of bothmagnitudes, whereby said quotient is indicative of the workpieceunbalance regardless of the weight of the workpiece.

Baker Apr. 6, 1943 Federn et a1 Sept. 16, 1958

1. A MACHINE FOR DETEMINING UNBALANCE OF A ROTATING WORKPIECE,COMPRISING AN OSCILLATORILY MOUNTED STRUCTURE HAVING SHAFT MEANS FORROTATING THE WORKPIECE ON SAID STRUCTURE, SAID STRUCTURE BEING CAPABLEOF OSCILLATION IN A PLANE PARALLEL TO THAT OF THE WORKPIECE ROTATION INRESPONSE TO UNBALANCE OF THE WORKPIECE, AN AUXILIARY OSCILLATORCORRESPONDING TO A KNOWN UNBALANCE, SYNCHRONIZING MEANS INTERCONNECTINGSAID SHAFT MEANS AND SAID OSCILLATOR FOR SYNCHRONIZING THE RESPECTIVEOSCILLATIONS OF SAID STRUCTURE AND SAID OSCILLATOR IN PHASE WITH EACHOTHER, SAID OSCILLATOR BEING MECHANICALLY COUPLED WITH SAID STRUCTURERELATIVE TO A GIVEN DIRECTION WHEREBY SAID RESPECTIVE OSCILLATIONSCOMBINE TO A CUMULATIVE RESULTANT OSCILLATION IN SAID DIRECTION, A FIRSTOSCILLATION PICKUP RESPONSIVE TO SAID RESULTANT OSCILLATION IN SAIDDIRECTION TO FURNISH AN OUT-